Hadrosaurid dinosaurs, the dominant large-bodied terrestrial herbivores in most Laurasian Late Cretaceous ecosystems, have an exceptional fossil record consisting of many species known from partial ontogenetic series, making them an ideal clade with which to conduct life-history studies. Previous research considered the Dinosaur Park Formation (DPF) of Alberta as an attritional, or time-averaged, sample and interpreted size–frequency distribution of long bones collected from the DPF with three size classes to suggest that hadrosaurids from the DPF attained near-asymptotic body size in under 3 years. This conflicted with previously published osteohistological estimates of 6+ years for penecontemporaneous hadrosaurids from the Two Medicine Formation (TMF) of Montana, suggesting either extreme variation in hadrosaurid growth rates or that size–frequency distributions and/or osteohistology and growth modeling inaccurately estimate ontogenetic age.We tested the validity of the previously proposed size–age relationship of hadrosaurids from the DPF by significantly increasing sample size and combining data from size–frequency distributions and osteohistology across multiple long-bone elements. The newly constructed size–frequency distributions typically reveal four relatively distinct size–frequency peaks that, when integrated with the osteohistological data, aligned with growth marks. The yearling size class was heavily underrepresented in the size–frequency distribution. If not due to preservation, this suggests that either juvenile (<2 years of age) hadrosaurids from the DPF had increased survivorship following an initially high nestling mortality rate or that yearlings were segregated from adults. A growth-curve analysis revealed asymptotic body size was attained in approximately 7 years, which is consistent with hadrosaurids from the TMF. The data suggest size–frequency distributions of attritional samples underestimate age and overestimate growth rates, but when paired with osteohistology can provide unique life-history insights.

中文翻译：

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测试大小频率分布作为个体发育衰老的方法：对加拿大阿尔伯塔省恐龙公园组鸭嘴龙科恐龙的生活史评估，对鸭嘴龙科古生态学有影响

鸭嘴龙类恐龙是劳亚晚期白垩纪生态系统中占主导地位的大型陆生食草动物，拥有特殊的化石记录，其中包括从部分个体发生系列中已知的许多物种，使其成为进行生活史研究的理想进化枝。先前的研究将阿尔伯塔省的恐龙公园组 (DPF) 视为从 DPF 收集的具有三个大小等级的长骨的磨损或时间平均样本和解释的大小-频率分布，以表明来自 DPF 的鸭嘴龙类达到近乎渐近3岁以下的体型。这与先前发表的来自蒙大拿州两药组 (TMF) 的准同期鸭嘴龙科的 6 年以上的骨组织学估计相矛盾，表明鸭嘴龙类生长速率的极端变化或大小 - 频率分布和/或骨组织学和生长模型不准确地估计个体发育年龄。我们通过显着增加样本量并结合来自多个长骨元素的大小频率分布和骨组织学数据。新构建的尺寸-频率分布通常显示四个相对不同的尺寸-频率峰值，当与骨组织学数据整合时，这些峰值与生长标记对齐。一岁鸽的体型在体型频率分布中的代表性严重不足。如果不是由于保存，这表明无论是少年（< 2 岁）来自 DPF 的鸭嘴龙类在最初的雏鸟死亡率很高或一岁仔与成年仔分开后，存活率有所提高。生长曲线分析显示在大约 7 年内达到渐近体型，这与来自 TMF 的鸭嘴龙科一致。数据表明，磨损样本的大小-频率分布低估了年龄而高估了增长率，但与骨组织学相结合可以提供独特的生活史见解。